/*
 *  Licensed to the Apache Software Foundation (ASF) under one or more
 *  contributor license agreements.  See the NOTICE file distributed with
 *  this work for additional information regarding copyright ownership.
 *  The ASF licenses this file to You under the Apache License, Version 2.0
 *  (the "License"); you may not use this file except in compliance with
 *  the License.  You may obtain a copy of the License at
 *
 *      http://www.apache.org/licenses/LICENSE-2.0
 *
 *  Unless required by applicable law or agreed to in writing, software
 *  distributed under the License is distributed on an "AS IS" BASIS,
 *  WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 *  See the License for the specific language governing permissions and
 *  limitations under the License.
 */

package org.apache.tomcat.jni;

/**
 * Lock
 *
 * @author Mladen Turk
 */
public class Lock {

	/**
	 * Enumerated potential types for APR process locking methods
	 * <br><b>Warning :</b> Check APR_HAS_foo_SERIALIZE defines to see if the platform supports
	 * APR_LOCK_foo.  Only APR_LOCK_DEFAULT is portable.
	 */

	public static final int APR_LOCK_FCNTL = 0;
	/**
	 * fcntl()
	 */
	public static final int APR_LOCK_FLOCK = 1;
	/**
	 * flock()
	 */
	public static final int APR_LOCK_SYSVSEM = 2;
	/**
	 * System V Semaphores
	 */
	public static final int APR_LOCK_PROC_PTHREAD = 3;
	/**
	 * POSIX pthread process-based locking
	 */
	public static final int APR_LOCK_POSIXSEM = 4;
	/**
	 * POSIX semaphore process-based locking
	 */
	public static final int APR_LOCK_DEFAULT = 5; /** Use the default process lock */

	/**
	 * Create and initialize a mutex that can be used to synchronize processes.
	 * <br><b>Warning :</b> Check APR_HAS_foo_SERIALIZE defines to see if the platform supports
	 * APR_LOCK_foo.  Only APR_LOCK_DEFAULT is portable.
	 *
	 * @param fname A file name to use if the lock mechanism requires one.  This
	 *              argument should always be provided.  The lock code itself will
	 *              determine if it should be used.
	 * @param mech  The mechanism to use for the interprocess lock, if any; one of
	 *              <PRE>
	 *              APR_LOCK_FCNTL
	 *              APR_LOCK_FLOCK
	 *              APR_LOCK_SYSVSEM
	 *              APR_LOCK_POSIXSEM
	 *              APR_LOCK_PROC_PTHREAD
	 *              APR_LOCK_DEFAULT     pick the default mechanism for the platform
	 *              </PRE>
	 * @param pool  the pool from which to allocate the mutex.
	 * @return Newly created mutex.
	 */
	public static native long create(String fname, int mech, long pool)
			throws Error;

	/**
	 * Re-open a mutex in a child process.
	 * This function must be called to maintain portability, even
	 * if the underlying lock mechanism does not require it.
	 *
	 * @param fname A file name to use if the mutex mechanism requires one.  This
	 *              argument should always be provided.  The mutex code itself will
	 *              determine if it should be used.  This filename should be the
	 *              same one that was passed to apr_proc_mutex_create().
	 * @param pool  The pool to operate on.
	 * @return Newly opened mutex.
	 */
	public static native long childInit(String fname, long pool)
			throws Error;

	/**
	 * Acquire the lock for the given mutex. If the mutex is already locked,
	 * the current thread will be put to sleep until the lock becomes available.
	 *
	 * @param mutex the mutex on which to acquire the lock.
	 */
	public static native int lock(long mutex);

	/**
	 * Attempt to acquire the lock for the given mutex. If the mutex has already
	 * been acquired, the call returns immediately with APR_EBUSY. Note: it
	 * is important that the APR_STATUS_IS_EBUSY(s) macro be used to determine
	 * if the return value was APR_EBUSY, for portability reasons.
	 *
	 * @param mutex the mutex on which to attempt the lock acquiring.
	 */
	public static native int trylock(long mutex);

	/**
	 * Release the lock for the given mutex.
	 *
	 * @param mutex the mutex from which to release the lock.
	 */
	public static native int unlock(long mutex);

	/**
	 * Destroy the mutex and free the memory associated with the lock.
	 *
	 * @param mutex the mutex to destroy.
	 */
	public static native int destroy(long mutex);

	/**
	 * Return the name of the lockfile for the mutex, or NULL
	 * if the mutex doesn't use a lock file
	 */
	public static native String lockfile(long mutex);

	/**
	 * Display the name of the mutex, as it relates to the actual method used.
	 * This matches the valid options for Apache's AcceptMutex directive
	 *
	 * @param mutex the name of the mutex
	 */
	public static native String name(long mutex);

	/**
	 * Display the name of the default mutex: APR_LOCK_DEFAULT
	 */
	public static native String defname();

}
